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1 In computer programming

In computer programming, when one compares the two values x and y, a negative number often indicates x < y, zero x == y and a positive number x > y. Even when two values are not integers, e.g. literal strings, this convention is largely adopted. For example, strcmp returns -1, 0, or 1 according to the lexicographical order, and qsort expects the comparison function to return values according to this convention. This is because it is efficient to do the subtraction x - y resulting in the directional signs above. In sorting algorithms, the efficiency of comparison code is critical since it is one of the major factors of sorting performance.

Sometimes, particularly in object-oriented programming, the comparison raises questions of datatypes and inheritance, equality and identity. It is often necessary to distinguish between:

• two objects with different datatypes both related to another datatype, e.g. an orange and a lemon, both being citrus fruit
• two different objects of the same type, e.g. two hands
• two objects being equal but distinct, e.g. two $10 banknotes
• two different references to the same object, e.g. two nicknames for the same person

Sameness and difference can be relative or graduated as well as absolute, particularly in fuzzy logic, artificial intelligence, signal processing, lossy data compression and pattern recognitionFor the William Gibson novel, see Pattern Recognition (novel). Pattern recognition (also known as classification or pattern classification) is a field within the area of computer science and can be defined as "the act of taking in raw data and taking an a.

See also: regular expressionA regular expression (abbreviated as regexp regex or by some regxp is a string that describes a whole set of strings, according to certain syntax rules. These expressions are used by many text editors and utilities (especially in the Unix operating system

2 In grammar

Comparison, in grammarThis article is about grammar from a linguistic perspective. For English grammar rules see English writing style According to the structuralist point of view, grammar is the study of the rules governing the use of a language. That set of rules is also cal, is a property of adjectiveAn adjective is a part of speech which modifies a noun, usually making its meaning more specific. Adjectives are used in a predicative or attributive manner. In some languages, attributive adjectives precede the noun. This is the case in the Germanic langs and adverbAn adverb is a part of speech that normally serves to modify verbs, adjectives, other adverbs, clauses, and sentences. Adverbs answer such questions as how when where in what way or how often In English, adverbs often have the suffix ly but so do many adjs in most languageAs with any complex, emergent concept, language is somewhat resistant to definition; however, most would agree that language is a system of communication or reasoning using representation along with metaphor and some manner of logical grammar. Many languas; it describes systems that distinguish the degree to which the modifier modifies its complement.

The second system of comparison in English appends the grammatical particles more and most, themselves the irregular comparatives of many, to the adjective or adverb being modified. This series can be compared to a system containing the diminutives less and least. This system is most commonly used with words of French or Latin derivation; adjectives and adverbs formed with suffixes other than -ly (e.g. beautiful); and with longer, technical, or infrequently used words. Knowing which words fall into which system is a highly idiomatic issue in English syntax. Some words require the suffixing system: e.g. taller is required; *more tall is not idiomatic English. Some words (e.g. difficult) require more and most. Some words (e.g. polite) can be used with either system; curiously, while polite can go either way, the derived word impolite requires more and most. The general rule is that words with one syllable require the suffix, words with three or more syllables require more or most and words with two syllables can go either way.

A perennial issue in English usage involves the comparison of so called "absolute" adjectives, the use of terms of comparison with words that in logic are not thought to admit of comparison. There are, of course, many adjectives that admit of no comparison, chiefly because the qualities they name are either present or absent; nothing is *more Cretaceous or *more igneous. The issue arises with words such as perfect, which according to the prescriptivists is another quality that does not admit of comparison; either something is perfect or it is not. Since true perfection is unachievable in the sublunary sphere, people like the drafters of the Constitution of the United States are constantly saying things like form a more perfect union; what they mean, of course, is more nearly perfect, and this is what the usage prescriptivists think they should have written. Since good writers and important leaders have used the contested form, the prescriptivists are bucking a well established usage here; in practice, the contested form is understood without error.